乳酸菌组合发酵菌种配方及其增殖培养基的优化

为了将甘肃牧区优良乳酸菌株用于直投式酸奶发酵剂的生产,以从甘肃牧区分离所得的乳酸乳球菌乳脂亚种(HM 598685)、嗜酸乳杆菌(HM 598684)、干酪乳杆菌(HM 598683),按照1:0:0、0:1:0、0:0:1、1:1:0、1:2:0、2:1:0、1:0:1、1:0:2、2:0:1、1:1:1、1:2:1、2:1:1、1:1:2的比例进行混合发酵,通过所制酸奶的感官性状和生化特性确定组合发酵的菌种配方,并对混合发酵的增殖培养基进行优化。结果发现,当3株菌比例为1:1:1时,其混合发酵的凝乳时间最短,为8.5h;所得酸奶的活菌数最大,高达7.90×10~8CFU/mL;而其感官评价中滋味气味及组织形态均显著优于其他组合。根据美蓝实验,当基础培养基中使用胰蛋白酶水解乳蛋白时,培养所得乳酸菌的活性最高,且活菌数可达2.93×10~8CFU/mL。通过L_9(3~4)正交设计,确定最佳增殖因子为酵母粉1%、果糖0.5%、吐温0.2%、乙酸钠0.5%,此时培养所得混合菌活菌数达2.11×10~9CFU/mL;各增殖因子对活菌数影响的主次顺序为:酵母粉>乙酸钠>果糖>吐温。

Formula of Mixed Fermentation of Lactic Acid Bacteria and Optimization of Enrichment Medium

In order to apply excellent lactic acid bacteria strains from pastoral area from Gansu province to production of direct vat set starter(DVS),Lactococcus lactis subspecies(HM 598683),Lactobacillus acidophilus(HM 598684) and Lactobacillus casei(HM 598685) from Gansu province were implemented in mixed fermentation by 1: 0:0,0:1:0,0:0:1,1:1:0,1:2:0,2:1:0,1:0:1,1:0:2,2:0:1,1:1:1,1:2:1,2:1:1,1:1:2,the formula of mixed fermentation was determined through sensory attributes and biochemical characteristics.And the enrichment medium of mixed fermentation was also optimized.The results showed that curd time was minimum with 8.5 h,the colony forming unit(CFU) was maximum with 7.90×10~8 CFU/mL and flavour and shape in sensory attributes was best when the ratio of strains was 1:1:1.According to methylene blue test,the activity of lactic acid bacteria was highest when trypsin was selected for hydrolyzing milk protein and the CFU was up to 2.93×10~8 CFU/mL.The optimum multiplication factors were determined by using L_9(3~4) orthogonal design with the CFU up to 2.11×10~9CFU/ mL,which were yeast powder 1%,fructose 0.5%,Tween 0.2%,sodium acetate 0.5%.The rank of effect of multiplication factors on CFU was yeast powder > sodium acetate > fructose > Tween.